This invention relates to novel substituted phenylacetic acid compounds which are useful as an acylating agent for preparing 3-acylamino-2-azetidinone compounds, especially, Nocardicin A having the following formula: ##STR2## Nocardicin A is valuable antibiotic especially against pathogenic Pseudomonas species and first produced by fermentation, and U.S. patent application covering the same was filed under Ser. No. 458,211 and granted under U.S. Pat. No. 3,923,977.
Further, U.S. patent application covering 3-acylamino-2-azetidinone compounds was filed on July 7, 1975 under Ser. No. 593,668 which is now abandoned, and C.I.P. application of it was filed on June 10, 1976 under Ser. No. 694,891, now abandoned. In the specification of said U.S. patent application Ser. No. 593,668, there are disclosed many 3-acylamino-2-azetidinones and an acylation process for preparation thereof. However in said specification, any specific object compounds per se of this invention are not disclosed as acylating agent, although the object compounds of this invention is only generically or sub-generically disclosed without specific descriptions therein.
Furthermore, in the prior specification, there are disclosed a few 3-acylamino-2-azetidinone compounds prepared by acylation of 3-amino-2-azetidinone compounds with the acylating agent which is structurally-close to the object compounds of this invention (see Example Nos. 96 and 97 of U.S. patent application Ser. No. 694,891). However, these compounds (i.e. Example Nos. 96 and 97), can not be used as a synthetic intermediate for Nocardicin A because the .alpha.-methoxyimino function of their 3-acyl groups can hardly be transformed into hydroxyimino function without any undesired degradations of their foundamental molecules such as cleavage of 2-azetidinone ring, elimination of 3-acyl group, etc.
Under the above state of prior art, in order to prepare Nocardicin A and other analogous compounds by chemical synthesis, inventors of this invention have investigated extensively and resulted successfully in synthesizing a useful starting acylating agent (i.e. object compounds of this invention) for preparing Nocardicin A and the other analogues.
Accordingly, the object compounds of this invention are characterized by substituted phenylacetic acid compounds having a protected amino group and/or a protected carboxy group, there protective groups of which are capable of being easily eliminated under mild reaction conditions.
The above successful synthesis of the substituted phenylacetic acid compounds thus realized have firstly provided new preparation method of Nocardicin A by chemical synthesis in addition to the prior fermention method.